Carbon nanotubes (CNTs) have been envisaged to have tremendous applications in the fields of sensors, medical diagnostics and therapeutics, chemical process control industry, nano-electronics, and nanoscale devices. In general, single-walled nanotubes (SWNTs) have been classified into metallic (m) and semiconducting (s) types, based on their chirality and n, m indices. Present methods of synthesis produce a mixture of metallic single walled carbon nanotubes (mSWNTs) and semiconducting single walled carbon nanotubes (sSWNTs), which in their native state self organize to form bundles of nanotubes of native SWNTs. However, for fabrication of a nanoelectronics device, it is essential to have only one type of SWNTs-either metallic or semiconducting type. From the native SWNTs (which always contain a mixture of mSWNTs and sSWNTs), it is impossible to make a semiconducting bundle of nanotubes. Selective destruction of mSWNTs in bundles of nanotubes makes fabrication of field effect transistors (FETs) with remaining sSWNTs possible.
Subramaniam C, et al. (2007), in “Visible fluorescence induced by the metal semiconductor transition in composites of carbon nanotubes with noble metal nanoparticles,” Phys. Rev. Lett. 99:167404-167407, states, “We show that single-walled carbon nanotube (SWNT) bundles emit fluorescence in the presence of noble metal nanoparticles and nanorods in the solid state. Conductivity measurements with metallic nanotubes, isolated from pristine SWNTs, show that they become semiconducting in the presence of metal nanoparticles.” It is, however, desirable to create a mSWNT-noble metal nanoparticle composite that exhibits semiconducting properties such that the composite reverts to metallic state reversibly.